Torque measurement using millimeter-wave metamaterial

Abstract

A method of determining a torque applied to a rotatable shaft is provided. The method includes transmitting a first electro-magnetic transmit signal towards a first mutually coupled structure mechanically coupled to the rotatable shaft, converting, by the first mutually coupled multitrack structure, the first electro-magnetic transmit signal into a first electro-magnetic receive signal; receiving the first electro-magnetic receive signal; evaluating the received first electro-magnetic receive signal; and determining the torque applied to the rotatable shaft based on the evaluated first electro-magnetic receive signal.

What is claimed is: 
     
       1. A torque measurement system, comprising:
 a first rotatable carrier structure mechanically coupled to a rotational shaft and configured to rotate about a rotational axis in a rotation direction; 
 a second rotatable carrier structure mechanically coupled to the rotational shaft and configured to rotate about the rotational axis in the rotation direction, wherein the second rotatable carrier structure is spaced apart from the first rotatable carrier structure; 
 a first metamaterial track coupled to the first rotatable carrier structure, wherein the first metamaterial track is arranged outside of the rotational axis, and wherein the first metamaterial track comprises a first array of elementary structures; 
 a second metamaterial track coupled to the second rotatable carrier structure, wherein the second metamaterial track is arranged outside of the rotational axis, and wherein the second metamaterial track comprises a second array of elementary structures, 
 wherein the first metamaterial track and the second metamaterial track are mutually coupled to each other by a first torque dependent coupling, thereby forming a first mutually coupled structure; 
 at least one transmitter configured to transmit a first electro-magnetic transmit signal towards the first mutually coupled structure, wherein the first mutually coupled structure is arranged to convert the first electro-magnetic transmit signal into a first electro-magnetic receive signal based on a torque applied to the rotational shaft; and 
 at least one receiver configured to receive the first electro-magnetic receive signal. 
 
     
     
       2. The torque measurement system of  claim 1 , wherein the first metamaterial track and the second metamaterial track are spaced apart by a first predetermined distance. 
     
     
       3. The torque measurement system of  claim 2 , wherein:
 the first rotatable carrier structure mechanically is coupled to the rotational shaft at a first point of attachment and the second rotatable carrier structure mechanically is coupled to the rotational shaft at a second point of attachment, and 
 the first point of attachment and the second point of attachment are spaced apart by a second predetermined distance that is greater than the first predetermined distance. 
 
     
     
       4. The torque measurement system of  claim 2 , further comprising:
 a flexible spacer interposed between the first rotatable carrier structure and the second rotatable carrier structure, wherein the flexible spacer defines the first predetermined distance. 
 
     
     
       5. The torque measurement system of  claim 1 , wherein the first torque dependent coupling affects an mm-wave property of the first mutually coupled structure such that the mm-wave property changes based on the torque applied to the rotational shaft. 
     
     
       6. The torque measurement system of  claim 5 , wherein the first torque dependent coupling includes at least one of capacitive near field coupling, inductive near field coupling, waveguide coupling, or far field coupling. 
     
     
       7. The torque measurement system of  claim 5 , wherein:
 the first mutually coupled structure is configured to modify the first electro-magnetic transmit signal based on the first torque dependent coupling, thereby producing the first electro-magnetic receive signal having a first property unique to the torque applied to the rotational shaft, and 
 the torque measurement system further comprises at least one processor configured to determine the torque applied to the rotational shaft based on the received first electro-magnetic receive signal, 
 wherein the at least one processor is configured to evaluate the first property of the received first electro-magnetic receive signal, and determine the torque applied to the rotational shaft based on the evaluated first property. 
 
     
     
       8. The torque measurement system of  claim 1 , wherein, in response to the torque applied to the rotational shaft, the first metamaterial track and the second metamaterial track are configured to rotate about the rotational axis by differing amounts causing a torque dependent shift in angular position between the first metamaterial track and the second metamaterial track and resulting in a torque dependent change to the first torque dependent coupling. 
     
     
       9. The torque measurement system of  claim 1 , wherein:
 the first metamaterial track is arranged at least partially around the rotational axis and a coupling effect between elementary structures of the first array of elementary structures is constant around a perimeter of the first metamaterial track, and 
 the second metamaterial track is arranged at least partially around the rotational axis and a coupling effect between elementary structures of the second array of elementary structures is constant around a perimeter of the second metamaterial track. 
 
     
     
       10. The torque measurement system of  claim 1 , wherein:
 the first mutually coupled structure is configured to convert the first electro-magnetic transmit signal into the first receive signal based on the first torque dependent coupling by at least one of partial reflection or partial absorption, and 
 the first electro-magnetic receive signal is either a partially-reflected signal of the first transmit signal that is reflected by the first mutually coupled structure or a partially-transmitted signal of the first transmit signal that passes through the first mutually coupled structure. 
 
     
     
       11. The torque measurement system of  claim 1 , further comprising:
 at least one processor configured to determine the torque applied to the rotational shaft based on the received first electro-magnetic receive signal. 
 
     
     
       12. The torque measurement system of  claim 11 , wherein:
 the receiver is configured to demodulate the received first electro-magnetic receive signal to generate a demodulated signal, and 
 the at least one processor is configured to evaluate a property of the received first electro-magnetic receive signal using at least one of phase analysis, amplitude analysis, or spectral analysis, and determine the torque applied to the rotatable shaft based on the evaluated property. 
 
     
     
       13. The torque measurement system of  claim 1 , further comprising:
 a third metamaterial track coupled to the first rotatable carrier structure, wherein the third metamaterial track is arranged around the rotational axis, and wherein the third metamaterial track comprises a third array of elementary structures, 
 wherein the at least one transmitter is configured to transmit a second electro-magnetic transmit signal at the third metamaterial track, wherein the third metamaterial track is arranged to convert the second electro-magnetic transmit signal into a second electro-magnetic receive signal, 
 the at least one receiver is configured to receive the second electro-magnetic receive signal. 
 
     
     
       14. The torque measurement system of  claim 13 , wherein:
 the third metamaterial track is configured to modify the second electro-magnetic transmit signal, thereby producing the second electro-magnetic receive signal having a property unique to an angular position of the third metamaterial track at which the second electro-magnetic transmit signal is incident, and 
 the torque measurement system further comprises at least one processor configured to evaluate the property of the received second electro-magnetic receive signal, and determine a first rotational position of the first rotatable carrier structure based on the evaluated property. 
 
     
     
       15. The torque measurement system of  claim 13 , further comprising:
 at least one processor configured to determine a first position change of the first rotatable carrier structure based on the second electro-magnetic receive signal. 
 
     
     
       16. The torque measurement system of  claim 15 , further comprising:
 a fourth metamaterial track coupled to the second rotatable carrier structure, wherein the fourth metamaterial track is arranged around the rotational axis, and wherein the fourth metamaterial track comprises a fourth array of elementary structures, 
 wherein the at least one transmitter is configured to transmit a third electro-magnetic transmit signal at the fourth metamaterial track, wherein the fourth metamaterial track is arranged to convert the third electro-magnetic transmit signal into a third electro-magnetic receive signal, 
 the at least one receiver is configured to receive the third electro-magnetic receive signal, and 
 the at least one processor is configured to determine a second position change of the second rotatable carrier structure based on the third electro-magnetic receive signal. 
 
     
     
       17. The torque measurement system of  claim 16 , wherein the at least one processor is further configured to determine a change of a rotational difference between the first rotatable carrier structure and the second rotatable carrier structure based on the first position change and the second position change. 
     
     
       18. The torque measurement system of  claim 17 , wherein:
 the at least one processor is configured to determine the torque applied to the rotational shaft based on the determined rotational difference. 
 
     
     
       19. The torque measurement system of  claim 1 , further comprising:
 a third metamaterial track coupled to the first rotatable carrier structure, wherein the third metamaterial track is arranged around the rotational axis, and wherein the third metamaterial track comprises a third array of elementary structures; and 
 a fourth metamaterial track coupled to the second rotatable carrier structure, wherein the fourth metamaterial track is arranged around the rotational axis, and wherein the fourth metamaterial track comprises a fourth array of elementary structures, 
 wherein the third metamaterial track and the fourth metamaterial track are mutually coupled to each other by a second torque dependent coupling, thereby forming a second mutually coupled structure, 
 wherein the at least one transmitter is configured to transmit a second electro-magnetic transmit signal towards the second mutually coupled structure, wherein the second mutually coupled structure is arranged to convert the second electro-magnetic transmit signal into a second electro-magnetic receive signal based on the torque applied to the rotational shaft, 
 wherein the at least one receiver is configured to receive the second electro-magnetic receive signal; and 
 at least one processor configured to determine the torque applied to the rotational shaft based on the received first electro-magnetic receive signal and the received second electro-magnetic receive signal. 
 
     
     
       20. The torque measurement system of  claim 19 , further comprising:
 at least one first isolation track coupled to the first rotatable carrier structure and interposed between the first metamaterial track and the third metamaterial track, wherein the at least one first isolation track is configured to isolate the first metamaterial track from the third metamaterial track; and 
 at least one second isolation track coupled to the second rotatable carrier structure and interposed between the second metamaterial track and the fourth metamaterial track, wherein the at least one second isolation track is configured to isolate the second metamaterial track from the fourth metamaterial track. 
 
     
     
       21. The torque measurement system of  claim 1 , wherein the first electro-magnetic transmit signal and the first electro-magnetic receive signal are electro-magnetic signals having wavelengths that reside in an electromagnetic spectrum. 
     
     
       22. The torque measurement system of  claim 1 , wherein the first electro-magnetic transmit signal and the first electro-magnetic receive signal are electromagnetic millimeter waves having frequencies in a millimeter frequency band. 
     
     
       23. The torque measurement system of  claim 1 , wherein the first array of elementary structures are arranged in a first grid array having first rows and first columns and the second array of elementary structures are arranged in a second grid array having second rows and second columns. 
     
     
       24. The torque measurement system of  claim 1 , wherein:
 the first array of elementary structures are coupled to each other via at least one of capacitive coupling or inductive coupling, and 
 the second array of elementary structures are coupled to each other via at least one of capacitive coupling or inductive coupling. 
 
     
     
       25. A method of determining a torque applied to a rotatable shaft, the method comprising:
 transmitting a first electro-magnetic transmit signal towards a first mutually coupled structure mechanically coupled to the rotatable shaft, 
 converting, by the first mutually coupled multitrack structure, the first electro-magnetic transmit signal into a first electro-magnetic receive signal; 
 receiving the first electro-magnetic receive signal, wherein the first electro-magnetic transmit signal and the first electro-magnetic receive signal are electro-magnetic wave signals; 
 evaluating the received first electro-magnetic receive signal; and 
 determining the torque applied to the rotatable shaft based on the evaluated first electro-magnetic receive signal. 
 
     
     
       26. The method of  claim 25 , wherein:
 the first electro-magnetic receive signal has a first property depending on an amount of the torque applied to the rotatable shaft, 
 evaluating the received first electro-magnetic receive signal comprises evaluating the first property of the received first electro-magnetic receive signal, and 
 determining the torque applied to the rotatable shaft comprises determining the torque applied to the rotatable shaft based on the evaluated first property. 
 
     
     
       27. The method of  claim 25 , wherein:
 the first mutually coupled structure comprises a first metamaterial track arranged outside of a rotational axis about which the rotatable shaft rotates and a second metamaterial track arranged outside the rotational axis and spaced apart from the first metamaterial track, and 
 the first metamaterial track and the second metamaterial track are mutually coupled to each other by a first torque dependent coupling, thereby forming the first mutually coupled structure. 
 
     
     
       28. The method of  claim 27 , wherein the first torque dependent coupling affects an mm-wave property of the first mutually coupled structure such that the mm-wave property changes based on the torque applied to the rotational shaft. 
     
     
       29. The method of  claim 27 , wherein:
 converting the first electro-magnetic transmit signal into the first electro-magnetic receive signal comprises modifying the first electro-magnetic transmit signal based on the first torque dependent coupling, thereby producing the first electro-magnetic receive signal having a first property unique to the torque applied to the rotational shaft, 
 evaluating the received first electro-magnetic receive signal comprises evaluating the first property of the received first electro-magnetic receive signal, and 
 determining the torque applied to the rotational shaft comprises determining the torque applied to the rotational shaft based on the evaluated first property. 
 
     
     
       30. The method of  claim 29 , wherein evaluating the received first electro-magnetic receive signal comprises demodulating the received first electro-magnetic receive signal to generate a demodulated signal, and evaluating the first property of the demodulated signal using at least one of phase analysis, amplitude analysis, or spectral analysis.